About this 3D model

The delrin plunger, while an elegantly simple idea, bothers me a little because of the added drag on the filament. Even more so with the stepper driven mk6 extruder since for me at least there seems to be a pretty fine line between having it tight enough and too tight such that you are losing steps. Like jstkatz and his http://www.thingiverse.com/thing:7037 I didn't like having the 4 screws and springs. I wanted something a little little simpler and could more easily pivot out of the way. jstkatz's design definitely came out a little more elegant but functionally I think they are pretty similar (except mine uses the mk6 nema 17 motor).